Microglial Polarization Research Articles

MiR-34a-5p Predicts the Risk of Diabetic Neuropathic Pain and Mediates Neuroinflammation in Microglia via Targeting ENPP3

ABSTRACT Introduction The pathogenesis of diabetic neuropathic pain (DNP) is complex involving various processes, which need exploring reliable biomarkers for its early detection and severity prediction. Methods Study enrolled 181 patients diagnosed with diabetes, among which 74 patients developed DNP. Serum miR-34a-5p levels were compared between DNP patients and non-DNP patients by polymerase chain reaction (PCR), and the potential of miR-34a-5p in predicting the risk and discriminating patients with DNP was evaluated. The regulatory effect of miR-34a-5p on the inflammation, proliferation, and polarization of microglia was evaluated in HMC3 cells treated with high glucose. Results Upregulated miR-34a-5p was identified as a risk factor and discriminated DNP patients miR-34a-5p was positively correlated with the levels of triglyceride (r = 0.797), fasting blood glucose (r = 0.840), and glycated hemoglobin (r = 0.894) of DNP patients. In HMC3 cells, the high-glucose-induced inflammation, promoted cell growth and caused polarization. The knockdown of miR-34a-5p showed the significant protective effect of microglia activation by high glucose, which was reversed by silencing ENPP3. Discussion miR-34a-5p served as a biomarker for the prediction and early detection of DNP and mediated microglia inflammation caused by DNP via modulating ENPP3.

Chemerin 15 peptide reduces neuroinflammation via the ChemR23 receptor after ischemia-reperfusion injury.

Microglia-mediated neuroinflammation plays a crucial role in ischemic stroke; consequently, understanding its regulation could facilitate the development of therapies for ischemic stroke. Chemerin 15, a 15-amino acid peptide derived from chemerin, exerts powerful anti-inflammatory effects through ChemR23, modulates macrophage polarization, and diminishes inflammatory cytokine expression in peripheral inflammation models. However, its effects on microglia and stroke remain unclear. In this study, we used an in vitro oxygen/ glucose deprivation BV2 cell model and a mouse model of ischemia-reperfusion injury to investigate the role of chemerin 15 in stroke and the underlying mechanisms. We co-cultured BV2 microglial cells with HT-22 hippocampal neurons and observed that chemerin 15 reduced apoptosis in HT-22 cells. Furthermore, we found that chemerin 15 binds to the ChemR23 receptor on the cell surface, inducing its internalization. This process regulated the activity of adenosine 5'-monophosphate-activated protein kinase and inhibited its downstream target nuclear factor kappa B. These effects could be reversed by treatment with α-NETA, a ChemR23 inhibitor. In mice with ischemia-reperfusion injury, chemerin 15 modulated microglial polarization, reduced infarct volume and neuronal apoptosis, and facilitated cognitive and neurological function recovery. Our findings suggest that chemerin 15 suppresses the microglia-mediated inflammatory response, decreases neuronal apoptosis, and enhances long-term neurological function recovery by inducing ChemR23 internalization and regulating the adenosine 5'-monophosphate-activated protein kinase/nuclear factor kappa B signaling pathway.

Electroacupuncture reduces inflammatory damage following cerebral ischemia–reperfusion by enhancing ABCA1-mediated efferocytosis in M2 microglia

Ischemic stroke (IS) is a severe cerebrovascular disease with high disability and mortality rates, where the inflammatory response is crucial to its progression and prognosis. Efferocytosis, the prompt removal of dead cells, can reduce excessive inflammation after IS injury. While electroacupuncture (EA) has been shown to decrease inflammation post-ischemia/reperfusion (I/R), its link to efferocytosis is unclear. Our research identified ATP-binding cassette transporter A1 (Abca1) as a key regulator of the engulfment process of efferocytosis after IS by analyzing public datasets and validating findings in a mouse model, revealing its close ties to IS progression. We demonstrated that EA can reduce neuronal cell death and excessive inflammation caused by I/R. Furthermore, EA treatment increased Abca1 expression, prevented microglia activation, promoted M2 microglia polarization, and enhanced their ability to phagocytose injured neurons in I/R mice. This suggests that EA's modulation of efferocytosis could be a potential mechanism for reducing cerebral I/R injury, making regulators of efferocytosis steps a promising therapeutic target for EA benefits.

Mer activation ameliorates nerve injury-induced neuropathic pain by regulating microglial polarization and neuroinflammation via SOCS3 in male rats.

Accumulating evidence has demonstrated that M1 microglial polarization and neuroinflammation worsen the development of neuropathic pain. However, the mechanisms underlying microglial activation during neuropathic pain remain incompletely understood. Myeloid-epithelial-reproductive tyrosine kinase (Mer), which is a member of the Tyro-Axl-Mer (TAM) family of receptor tyrosine kinases, plays a crucial role in the regulation of microglial polarization. However, the effect of Mer on microglial polarization during neuropathic pain has not been determined. In this study, western blotting, immunofluorescence analysis, quantitative polymerase chain reaction (qPCR), and enzyme-linked immunosorbent assay (ELISA) were used to examine the role of Mer in pain hypersensitivity and microglial polarization in rats with chronic constriction injury (CCI) of the sciatic nerve. The results indicated that Mer expression in microglia was prominently increased in the spinal cords of rats subjected to CCI. Furthermore, treatment with recombinant protein S (PS, an activator of Mer) alleviated mechanical allodynia and thermal hyperalgesia, promoted the switch in microglia from the M1 phenotype to the M2 phenotype, and ameliorated neuroinflammation in rats subjected to CCI. However, the use of suppressor of cytokine signalling 3 (SOCS3) siRNA abolished these changes. These results indicated that Mer regulated M1/M2 microglial polarization and neuroinflammation and may be a potential target for treating neuropathic pain.

MicroRNA-125b-5p alleviated CCI-induced neuropathic pain and modulated neuroinflammation via targeting SOX11.

Increasing evidence demonstrated the involvement of microRNAs (miRNAs) in the onset and development of neuropathic pain (NP). Exploring the molecular mechanism underlying NP and identifying key molecules could provide potential targets for the therapy of NP. The function and mechanism of miR-125b-5p in regulating NP have been studied, aiming to find a potential therapeutic target for NP. NP rat models were established by the chronic constriction injury (CCI) method. The paw withdrawal threshold and paw withdrawal latency were assessed to evaluate the establishment and recovery of rats. Highly aggressive proliferating immortalized (HAPI) micoglia cell, a rat microglia cell line, was treated with lipopolysaccharide (LPS). The M1/M2 polarization and inflammation were evaluated by enzyme-linked immunosorbent assay and western blotting. Decreasing miR-125b-5p and increasing SOX11 were observed in CCI rats and LPS-induced HAPI cells. Overexpressing miR-125b-5p alleviated mechanical allodynia and thermal hyperalgesia and suppressed inflammation in CCI rats. LPS induced M1 polarization and inflammation of HAPI cells, which was attenuated by miR-125b-5p overexpression. miR-125-5p negatively regulated the expression of SOX11 in CCI rats and LPS-induced HAPI cells. Overexpressing SOX11 reversed the protective effects of miR-125b-5p on mechanical pain in CCI rats and the polarization and inflammation in HAPI cells, which was considered the mechanism underlying miR-125b-5p. miR-125b-5p showed a protective effect on NP by regulating inflammation and polarization of microglia via negatively modulating SOX11.

Inhibition of cGAS attenuates neonatal hypoxic-ischemic encephalopathy via regulating microglia polarization and pyroptosis.

Neonatal hypoxic-ischemic encephalopathy (HIE) is a condition causing brain injury in newborns with unclear pathogenesis. Cyclic GMP-AMP synthase (cGAS)/stimulator of interferon genes (STING) signaling pathway and NOD-like receptor protein 3 (NLRP3) mediated pyroptosis are thought to be involved in the pathological process of HIE, but whether these two mechanisms act independently is still unknown. Therefore, we aim to clarify whether there is any interaction between these two pathways and thus synergistically affects the progression of HIE. The HIE model of neonatal rats was established using the Rice-Vannucci method. The potential therapeutic effect of RU.521 targeting cGAS on HIE was explored through rescue experiment. Twenty-four hours after modeling was selected as observation point, sham + vehicle group, HIE + vehicle group and HIE + RU.521 group were established. A complete medium of BV2 cells was adjusted to a glucose-free medium, and the oxygen-glucose deprivation model was established after continuous hypoxia for 4 hours and reoxygenation for 12 to 24 hours. 2,3,5-triphenyl tetrazolium chloride staining was employed to detect ischemic cerebral infarction in rat brain tissue, and hematoxylin and eosin staining was used to observe tissue injury. Immunofluorescence was applied to monitor the expression of cGAS. Real-time quantitative polymerase chain reaction and western blot were utilized to detect the expression of messenger RNA and protein. cGAS expression was increased in brain tissues of neonatal rats with HIE, and mainly localized in microglia. RU.521 administration reduced infarct size and pathological damage in rat HIE. Moreover, blocking cGAS with RU.521 significantly reduced inflammatory conditions in the brain by down-regulating STING expression, decreasing NLRP3 inflammasome activation and reducing microglial pyroptosis both in vivo and in vitro. Besides, RU.521 promoted the switching of BV2 cells towards the M2 phenotype. This study revealed a link between the cGAS/STING pathway and the NLRP3/GSDMD/pyroptosis pathway in neonatal HIE. Furthermore, the small molecule compound RU.521 can negatively regulate cGAS/STING/NLRP3/pyroptosis axis and promote M2 polarization in microglia, which provides a potential therapeutic strategy for the treatment of neuroinflammation in HIE.

An active & passive dual-targeting platform for the precise treatment, process monitoring and effective protection of central nervous system infection

Precise antibacterial activity and effective inflammatory response reduction are critical for successful treatment of Intracranial infection after craniocerebral surgery, which remains an unmet clinical challenge. Herein, an intracranial drug delivery liposome (AFAA-lipo) that possesses dual active&passive targeting capability, direct antibacterial ability, favorable inflammation regulation, and excellent biocompatibility is developed as an antibiotics-free and hardly bacterial-resistance-induced platform for the management of intracranial infection. The surface-anchored specific peptide sequence HRERMS (the oligopeptide designed sourced from β-amyloid precursor protein) makes AFAA-lipo actively penetrate the blood–brain barrier and then perforated and lysed under the stimulation of α-toxin secreted by methicillin-resistant Staphylococcus aureus (MRSA, a severe and widespread intracranial infection type) in the infected site. Our results demonstrate that the AFAA-lipo can eliminate bacteria and biofilms, and reduce inflammatory response through mitochondrial function protection, DNA preservation from damage, TNFR1/NF-κB signaling pathway inhibition, and promotion of microglial polarization towards the anti-inflammatory subtype, ultimately improving post-infection prognosis and survival rate. More interestingly, the pre-intake of AFAA-lipo is capable to reduce MRSA infection risk and alleviate inflammatory response. Furthermore, the near-infrared (NIR) II region imaging fluorescence signal intensity variations of AFAA-lipo is proved the validation to monitor the course of the disease.

Astaxanthin promotes nerve repair by regulating the M1/M2 ratio of microglia and promoting angiogenesis

Astaxanthin (ATX), a naturally occurring carotenoid, exhibits notable neuroprotective properties, including anti-inflammatory effects and regulation of neurotrophic factors. This study investigates the fundamental processes by which astaxanthin facilitates the repair of peripheral nerve injuries. Our experiments with in vivo and in vitro models reveal that astaxanthin treatment induces a shift from M1 to M2 microglial polarization and attenuates the inflammatory response in Schwann cells. However, these beneficial effects are negated by the inhibition of the STAT6-PPARγ pathway. Furthermore, astaxanthin administration mitigated gastrocnemius muscle atrophy in rats with peripheral nerve injuries and enhanced axonal regeneration and myelination. Notably, an increase in neovascularization was also observed post-treatment. In summary, astaxanthin significantly promotes nerve regeneration following peripheral nerve injury, highlighting its potential therapeutic value and underscoring the need for further clinical investigations.

Electroacupuncture regulates glucose metabolism by inhibiting SGLT1 levels, inhibiting microglial polarization, and alleviating Parkinson's disease

BackgroundParkinson's disease (PD) is a common central neurodegenerative disease in middle-aged and elderly people. The progressive degeneration and death of dopaminergic neurons leads to insufficient dopamine (DA) neurotransmitters. Acupuncture and moxibustion can alleviate the aging of neurons. Therefore, studying the neuroprotective effects of electroacupuncture (EA) in PD mice is particularly important. MethodsIntraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 20 mg/kg) was used to establish a PD mouse model, and lipopolysaccharide (LPS) was used to induce microglia polarization. Western blotting, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL), Nissl staining and immunohistochemistry were used to detect neuronal apoptosis and injury, α-syn expression and microglial accumulation in PD mice. In addition, the levels of inflammatory factors were determined using enzyme-linked immunosorbent assay (ELISA). Flow cytometry was used to detect the Ca2+ content. The fluorescein isothiocyanate (FITC) labeling method was used to assess glucose uptake. A reagent kit was used to detect glucose and lactate levels. ResultsMPTP induced the selective loss of DA neurons in the SN of mice, altered Ca2+ homeostasis, and induced an inflammatory response. In addition, maintaining Ca2+ homeostasis depends on the activity of transient receptor potential channel 1 (TRPC1). EA therapy promotes TRPC1 expression, which has a negative regulatory effect on sodium–glucose cotransporter 1 (SGLT1). Under the action of EA, TRPC1 protein expression increased, Ca2+ concentrations increased, and the effect of SGLT1 was inhibited, thereby facilitating glucose metabolism, blocking the activation of the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway, restraining M1 polarization of microglia, and alleviating the PD process. ConclusionEA promotes TRPC1/Ca2+ pathway activation, inhibits SGLT1-mediated regulation of glucose metabolism and PI3K/AKT pathway activation, inhibits microglial M1 polarization, and alleviates PD.

Inhibiting the NF-κB/DRP1 Axis Affords Neuroprotection after Spinal Cord Injury via Inhibiting Polarization of Pro-Inflammatory Microglia.

Spinal cord injury (SCI) is considered a central nervous system (CNS) disorder. Nuclear factor kappa B (NF-κB) regulates inflammatory responses in the CNS and is implicated in SCI pathogenesis. The mechanism(s) through which NF-κB contributes to the neuroinflammation observed during SCI however remains unclear. SCI rat models were created using the weight drop method and separated into Sham, SCI and SCI+NF-κB inhibitor groups (n = 6 rats per-group). We used Hematoxylin-Eosin Staining (H&E) and Nissl staining for detecting histological changes in the spinal cord. Basso-Beattie-Bresnahan (BBB) behavioral scores were utilized for assessing functional locomotion recovery. Mouse BV2 microglia were exposed to lipopolysaccharide (LPS) to mimic SCI-induced microglial inflammation in vitro. Inhibition of NF-κB using JSH-23 alleviated inflammation and neuronal injury in SCI rats' spinal cords, leading to improved locomotion recovery (p < 0.05). NF-κB inhibition reduced expression levels of CD86, interleukin-6 (IL-6), IL-1β, and inducible Nitric Oxide Synthase (iNOS), and improved expression levels of CD206, IL-4, and tissue growth factor-beta (TGF-β) in both LPS-treated microglia and SCI rats' spinal cords (p < 0.05). Inhibition of NF-κB also effectively suppressed mitochondrial fission, evidenced by the reduced phosphorylation of dynamin-related protein 1 (DRP1) at Ser616 (p < 0.001). We show that inhibition of the NF-κB/DRP1 axis prevents mitochondrial fission and suppresses pro-inflammatory microglia polarization, promoting neurological recovery in SCI. Targeting the NF-κB/DRP1 axis therefore represents a novel approach for SCI.

Müller Cells Harboring Exosomal lncRNA OGRU Modulate Microglia Polarization in Diabetic Retinopathy by Serving as miRNA Sponges.

Diabetic retinopathy (DR) is one of the most common complications of diabetes mellitus which is associated with visual loss and blindness worldwide. However, the effective treatments for both early- and late-stage DR remains lacking. A streptozotocin (STZ)-induced diabetic mice model and high glucose (HG)-treated Müller cell model were established. M1/M2 microglia polarization was assessed by immunofluorescence (IF) staining and flow cytometry. Expression of lncRNA OGRU, cytokines and other key molecules were detected by qRT-PCR or western blot. ELISA assay was employed to monitor cytokine secretion. Müller cell-derived exosomes were isolated and characterized by nanopartical tracking analysis (NTA), western blot and transmission electron microscopy (TEM), and exosome uptake assay was used to monitor the intercellular transport of exosomes. Associations among lncRNA-miRNA-mRNA networks were validated by RNA pull-down and RNA immunoprecipitation (RIP) and dual luciferase assays. Increased M1 polarization but decreased M2 polarization of retinal microglia were observed in DR mice. HG-treated Müller cell-derived exosomes transported OGRU into microglia and promoted microglia polarization toward M1 phenotype. Mechanistically, OGRU served as a competing endogenous RNA (ceRNA) for miR-320-3p, miR-221-3p and miR-574-5p to regulate AR, PFKFB3 and GLUT1 expression in microglia, respectively. Loss of miR-320-3p/miR-221-3p/miR-574-5p or reinforced AR/PFKFB3/GLUT1 abrogated OGRU silencing-mediated microglia polarization in vitro. In vivo studies further showed that OGRU/miR-320-3p/AR, OGRU/miR-221-3p/PFKFB3 and OGRU/miR-574-5p/GLUT1 axes regulated microglia polarization in DR mice. Collectively, Müller cells-derived exosomal OGRU regulated microglia polarization in DR via modulating OGRU/miR-320-3p/AR, OGRU/miR-221-3p/PFKFB3 and OGRU/miR-574-5p/GLUT1 axes.

GsMTx4 ameliorates spinal cord injury by regulating microglial polarization through the Piezo1/NFκB/STAT6 pathway

ObjectiveInflammatory reactions are recognized as pivotal in spinal cord injury (SCI), with the anti-inflammatory role of polarized microglia crucial in mitigating such injury. The present study aimed to determine the protective effects of GsMTx4 on functional recovery in a mouse model of SCI and investigate the role of GsMTx4 in cytokine-induced microglial activation and associated molecular mechanisms. MethodsWe assessed the effects of GsMTx4 on motor function in a mouse model of SCI, including neuronal survival and activated microglia in the vicinity of the injury after SCI. We also investigated the effects of GsMTx4 on expression of relevant inflammatory factors involved in cytokine-induced microglial activation and the associated signaling pathways. ResultsGsMTx4 effectively promoted functional recovery in mice and alleviated nerve damage after SCI. Additionally, GsMTx4 facilitated the transition of microglia from the M1 phenotype to the M2 phenotype, suppressed microglial activation, and reduced the expression of corresponding inflammatory mediators. These effects may involve modulation of neurogenic inflammation through the Piezo1/NFκB/STAT6 pathway, at least in part. ConclusionGsMTx4 safeguards against SCI by regulating microglial polarization, potentially via the Piezo1/NFκB/STAT6 pathway, offering initial evidence supporting the potential therapeutic efficacy of GsMTx4 for treatment of SCI.

An Optimized Decellularized Extracellular Matrix from Dental Pulp Stem Cell Sheets Promotes Axonal Regeneration by Multiple Modes in Spinal Cord Injury Rats.

In the field of tissue engineering, the extracellular matrix (ECM) is considered an important element for promoting neural regeneration after spinal cord injury (SCI). Dental pulp stem cells (DPSCs), mesenchymal stem cells that originate from the neural crest, are easy to harvest and culture in vitro, express a variety of neurotrophic factors (NTFs) and deposit a large amount of ECM, making them a good choice for stem cell- or ECM-based treatment of SCI. In the present study, decellularized extracellular matrix (dECM) derived from DPSC sheets is used for the treatment of SCI. Optimization experiments reveal that incubating DPSC sheets with 1% Triton X-100 for 5 min is the best procedure for preparing DPSC dECM. It is found that DPSC dECM promotes nerve repair and regeneration after SCI and restores hindlimb motor function in rats. Mechanistically, DPSC dECM facilitates the migration and neural differentiation of neural stem cells, as well as M2 polarization of microglia, and inhibits the formation of glial scars. This study suggests that the use of DPSC dECM is a potential strategy for the treatment of SCI.

Increased Pan-Type, A1-Type, and A2-Type Astrocyte Activation and Upstream Inflammatory Markers Are Induced by the P2X7 Receptor.

This study asked whether the P2X7 receptor was necessary and sufficient to trigger astrocyte polarization into neuroinflammatory activation states. Intravitreal injection of agonist BzATP increased gene expression of pan-astrocyte activation markers Gfap, Steap4, and Vim and A1-type astrocyte activation markers C3, Serping1, and H2T23, but also the Cd14 and Ptx3 genes usually associated with the A2-type astrocyte activation state and Tnfa, IL1a, and C1qa, assumed to be upstream of astrocyte activation in microglia. Correlation analysis of gene expression suggested the P2X7 receptor induced a mixed A1/A2-astrocyte activation state, although A1-state genes like C3 increased the most. A similar pattern of mixed glial activation genes occurred one day after intraocular pressure (IOP) was elevated in wild-type mice, but not in P2X7-/- mice, suggesting the P2X7 receptor is necessary for the glial activation that accompanies IOP elevation. In summary, this study suggests stimulation of the P2X7R is necessary and sufficient to trigger the astrocyte activation in the retina following IOP elevation, with a rise in markers for pan-, A1-, and A2-type astrocyte activation. The P2X7 receptor is expressed on microglia, optic nerve head astrocytes, and retinal ganglion cells (RGCs) in the retina, and can be stimulated by the mechanosensitive release of ATP that accompanies IOP elevation. Whether the P2X7 receptor connects this mechanosensitive ATP release to microglial and astrocyte polarization in glaucoma remains to be determined.

Neuroprotective Effects of AER-271 in a tMCAO Mouse Model: Modulation of Autophagy, Apoptosis, and Inflammation.

Following ischemic stroke, aquaporin 4 (AQP4) expression modifications have been associated with increased inflammation. However, the underlying mechanisms are not fully understood. This study aims to elucidate the mechanistic basis of post-cerebral ischemia-reperfusion (I/R) inflammation by employing the AQP4-specific inhibitor, AER-271. The middle cerebral artery occlusion (MCAO) model was used to induce ischemic stroke in mice. C57BL/6 mice were randomly allocated into four groups: sham operation, I/R, AER-271, and 2-(nicotinamide)-1,3,4-thiadiazole (TGN-020) treatment, with observations recorded at 1day, 3days, and 7days post-tMCAO. Each group consisted of 15 mice. Procedures included histological examination through HE staining, neurological scoring, Western blot analysis, and immunofluorescence staining. AER-271 treatment yielded significant improvements in post-stroke weight recovery and neurological scores, accompanied by a reduction in cerebral infarction volume. Moreover, AER-271 exhibited a noticeable influence on autophagic and apoptotic pathways, affecting the activation of both pro-inflammatory and anti-inflammatory cytokines. Alterations in the levels of inflammatory biomarkers MCP-1, NLRP3, and caspase 1 were also detected. Finally, a comparative assessment of the effects of AER-271 and TGN-020 in mitigating apoptosis and microglial polarization in ischemic mice revealed neuroprotective effects with no significant difference in efficacy. This study provides essential insights into the neuroprotective mechanisms of AER-271 in cerebral ischemia-reperfusion injury, offering potential clinical applications in the treatment of ischemic cerebrovascular disorders.

Deacetylase SIRT2 Inhibition Promotes Microglial M2 Polarization Through Axl/PI3K/AKT to Alleviate White Matter Injury After Subarachnoid Hemorrhage.

White matter injury (WMI) subsequent to subarachnoid hemorrhage (SAH) frequently leads to an unfavorable patient prognosis. Previous studies have indicated that microglial M1 polarization following SAH results in the accumulation of amyloid precursor protein (APP) and degradation of myelin basic protein (MBP), thereby catalyzing the exacerbation of WMI. Consequently, transitioning microglial polarization towards the M2 phenotype (neuroprotective state) represents a potential therapeutic approach for reversing WMI. The SIRT2 gene is pivotal in neurological disorders such as neurodegeneration and ischemic stroke. However, its function and underlying mechanisms in SAH, particularly how it influences microglial function to ameliorate WMI, remain unclear. Our investigations revealed that in post-SAH, there was a temporal increase in SIRT2 expression, predominantly in the cerebral corpus callosum area, with notable colocalization with microglia. However, following the administration of the SIRT2 inhibitor AK-7, a shift in microglial polarization towards the M2 phenotype and an improvement in both short-term and long-term neuronal functions in rats were observed. Mechanistically, CO-IP experiments confirmed that SIRT2 can interact with the receptor tyrosine kinase Axl within the TAM receptor family and act as a deacetylase to regulate the deacetylation of Axl. Concurrently, the inhibition of SIRT2 by AK-7 can lead to increased expression of Axl and activation of the anti-inflammatory pathway PI3K/Akt signaling pathway, which regulates microglial M2 polarization and consequently reduces WMI. However, when Axl expression was inhibited by the injection of the shAxl virus into the lateral ventricles, the downstream signaling pathways were significantly suppressed. Rescue experiments also confirmed that the neuroprotective effects of AK-7 can be reversed by PI3K inhibitors. These data suggest that SIRT2 influences WMI by affecting microglial polarization through the Axl/PI3K/AKT pathway, and that AK-7 could serve as an effective therapeutic drug for improving neurological functions in SAH patients.

IL-23 Priming Enhances the Neuroprotective Effects of MSC-Derived Exosomes in Treating Retinal Degeneration.

Neuroinflammation is a characteristic feature of neurodegenerative diseases. Mesenchymal stem cell-derived exosomes (MSC-exo) have shown neuroprotective effects through immunoregulation, but the therapeutic efficacy remains unsatisfactory. This study aims to enhance the neuroprotective capacity of MSC-exo through IL-23 priming for treating retinal degeneration in mice. MSC were primed with IL-23 stimulation in vitro, and subsequently, exosomes (MSC-exo and IL-23-MSC-exo) were isolated and characterized. Two retinal degenerative disease models (NaIO3-induced mice and rd10 mice) received intravitreal injections of these exosomes. The efficacy of exosomes was assessed by examining retinal structural and functional recovery. Furthermore, exosomal microRNA (miRNA) sequencing was conducted, and the effects of exosomes on the M1 and M2 microglial phenotype shift were evaluated. IL-23-primed MSC-derived exosomes (IL-23-MSC-exo) exhibited enhanced capability in protecting photoreceptor cells and retinal pigment epithelium (RPE) cells against degenerative damage and fostering the restoration of retinal neural function in both NaIO3-induced retinal degeneration mice and rd10 mice when compared with MSC-exo. The exosomal miRNA suppression via Drosha knockdown in IL-23-primed MSC would abolish the neuroprotective role of IL-23-MSC-exo, highlighting the miRNA-dependent mechanism. Bioinformatic analysis, along with further in vivo biological studies, revealed that IL-23 priming induced a set of anti-inflammatory miRNAs in MSC-exo, prompting the transition of M1 to M2 microglial polarization. IL-23 priming presents as a potential avenue for amplifying the immunomodulatory and neuroprotective effects of MSC-exo in treating retinal degeneration.

Transplantation of miR-145a-5p modified M2 type microglia promotes the tissue repair of spinal cord injury in mice

BackgroundThe traumatic spinal cord injury (SCI) can cause immediate multi-faceted function loss or paralysis. Microglia, as one of tissue resident macrophages, has been reported to play a critical role in regulating inflammation response during SCI processes. And transplantation with M2 microglia into SCI mice promotes recovery of motor function. However, the M2 microglia can be easily re-educated and changed their phenotype due to the stimuli of tissue microenvironment. This study aimed to find a way to maintain the function of M2 microglia, which could exert an anti-inflammatory and pro-repair role, and further promote the repair of spinal cord injury.MethodsTo establish a standard murine spinal cord clip compression model using Dumont tying forceps. Using FACS, to sort microglia from C57BL/6 mice or CX3CR1GFP mice, and further culture them in vitro with different macrophage polarized medium. Also, to isolate primary microglia using density gradient centrifugation with the neonatal mice. To transfect miR-145a-5p into M2 microglia by Lipofectamine2000, and inject miR-145a-5p modified M2 microglia into the lesion sites of spinal cord for cell transplanted therapy. To evaluate the recovery of motor function in SCI mice through behavior analysis, immunofluorescence or histochemistry staining, Western blot and qRT-PCR detection. Application of reporter assay and molecular biology experiments to reveal the mechanism of miR-145a-5p modified M2 microglia therapy on SCI mice.ResultsWith in vitro experiments, we found that miR-145a-5p was highly expressed in M2 microglia, and miR-145a-5p overexpression could suppress M1 while promote M2 microglia polarization. And then delivery of miR-145a-5p overexpressed M2 microglia into the injured spinal cord area significantly accelerated locomotive recovery as well as prevented glia scar formation and neuron damage in mice, which was even better than M2 microglia transplantation. Further mechanisms showed that overexpressed miR-145a-5p in microglia inhibited the inflammatory response and maintained M2 macrophage phenotype by targeting TLR4/NF-κB signaling.ConclusionsThese findings indicate that transplantation of miR-145a-5p modified M2 microglia has more therapeutic potential for SCI than M2 microglia transplantation from epigenetic perspective.Graphical

Mesoporous manganese-doped nano-antioxidant suppresses pyroptosis for effective ischemic stroke therapy

Pyroptosis mediates neuroinflammation following ischemic stroke and contributes to its development, indicating that targeting pyroptosis-related pathways could be a potential therapeutic strategy for stroke. In this study, a mesoporous manganese-doped cerium oxide (MMC) nano-antioxidant encapsulated with caspase-1 inhibitor VX765 is rationally designed and engineered to relieve ischemic stroke by integrating the suppression of pyroptosis activity with reactive oxygen species (ROS) scavenging capability. Through the surface modification of Angiopoietin-2 (Ang2), the nano-antioxidant can specifically bind to the low-density lipoprotein receptor-related protein, cross the blood–brain barrier, and ultimately aggregate in ischemic neuronal tissues. In mice subjected to middle cerebral artery occlusion/reperfusion, the nano-antioxidant alleviates oxidative stress, inhibits cell pyroptosis, reduces inflammatory cytokines, and regulates microglial polarization toward M2, ultimately mitigating neuroinflammation and reperfusion injury in brain tissue. Mechanistic studies reveal that the pyroptosis-associated NOD-like receptor signaling pathway, the inflammation-associated TNF signaling pathway, the neutrophil chemotaxis-associated Toll-like receptor signaling pathway, and the oxidative stress-associated NF-kappa B signaling pathway are involved in the antioxidant-mediated stroke therapy. Endowed with pyroptosis-reversing ability and nano-antioxidant activities, this engineered antioxidant presents a novel therapeutic paradigm for minimizing reperfusion injury and enhancing stroke treatment efficacy.

IL-33 relieves nerve injury by mediating microglial polarization in neuromyelitis optica spectrum disorders via the IL-33/ST2 pathway

Interleukin-33 (IL-33) is a member of the interleukin-1 cytokine family. Its function in regulating microglial M1/M2 polarization in neuromyelitis optica spectrum disorder (NMOSD) is still unelucidated. To evaluate the role of IL-33 in NMOSD, we constructed NMOSD mice model by injecting purified serum IgG from AQP4-IgG seropositive NMOSD patients into experimental autoimmune encephalomyelitis (EAE) mice, and IL-33 was intraperitoneally injected into NMOSD mice 3 d before the model induction. We found that pretreatment of the NMOSD mice with IL-33 relieved brain neuron loss, and demyelination and improved the structure of axons, astrocytes, and mitochondria. In the neuronal and microglial coculture system, pretreatment with IL-33 in microglia alleviated NMOSD serum-induced inflammation and damaged morphology in cultured neurons. IL-33 transformed microglia to the M2 phenotype, and NMOSD serum promoted microglia to the M1 phenotype in cultured BV2 cells. Moreover, IL-33 influenced microglial polarity via the IL-33/ST2 pathway. IL-33 may be a novel insight useful for further developing NMOSD-targeted therapy and drug development.